Apparatus for supplying respiratory gas and a method for controlling the apparatus

ABSTRACT

An apparatus for supplying a respiratory gas includes a conveyor device for conveying the respiratory gas, a conduit for feeding the respiratory gas to a person, and a humidification device for humidifying the respiratory gas. A sensor device is configured to generate a signal indicative of the respiratory gas humidity and a control device is configured to control the humidification device with regard to the signal A method of supplying a respiratory gas to a patient, in which the respiratory gas is introduced by means of a conveyor device into the conduit leading to the patient and is humidified, includes operating the conveyor device so that a respiratory gas pressure which is above ambient pressure is provided in the conduit, and adjusting the humidity on the basis of signals indicative of the relative and/or absolute humidity of the respiratory gas generated by the sensor device.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/112,592, filed May 20, 2011, now U.S. Pat. No. 8,671,936, which is acontinuation of U.S. application Ser. No. 12/394,615, filed Feb. 27,2009, now U.S. Pat. No. 7,997,270, which is a continuation of U.S.application Ser. No. 10/487,570, filed Feb. 20, 2004, now U.S. Pat. No.7,516,740, which is the U.S. national phase of International ApplicationPCT/EP02/09147, filed Aug. 15, 2002 which designated the U.S. and claimspriority to German Application No. 101 39 881.6, filed Aug. 20, 2001,the entire contents of each of which are hereby incorporated byreference.

FIELD OF THE INVENTION

The invention concerns an apparatus for supplying a respiratory gas anda method of controlling the apparatus.

BACKGROUND OF THE INVENTION

In particular for the treatment of sleep-related breathing disorders, itis possible to supply the patient with a respiratory gas, for examplefiltered ambient air, at a pressure which is increased in relation tothe ambient pressure. A respiratory gas pressure which is in the rangeof between 4 and 18 mbar above the ambient pressure makes it possible toobviate obstructions in the region of the upper respiratory tracts.

It is possible for the pressure of the respiratory gas to be definedlyvaried. Thus it is possible in particular to control the pressure insuch a way that lower respiratory gas pressures obtained during theexpiration phases than during the inspiration phases. It is furtherpossible to adapt the respiratory gas pressure in such a way that forexample an increased respiratory gas pressure is only set when theperson to whom artificial respiration is to be given is in apredetermined stage in sleep. It is further possible for the respiratorygas supplied to the patient to be charged with selected additivesubstances and, in particular, humidified. Humidification of therespiratory gas can be effected by the gas being brought into contactwith warmed water. The degree of humidification of the respiratory gascan be adjusted in that case by way of the temperature of thehumidifying water.

SUMMARY OF THE INVENTION

The object of the invention is to provide an apparatus for and a methodof supplying a respiratory gas to a breathing person, whereby improvedphysiological compatibility of the supply of respiratory gas isachieved.

According to the invention that object is attained by an apparatushaving the features including a conveyor device for conveying therespiratory gas, a conduit for feeding the respiratory gas conveyed bythe conveyor device to a person, a humidification device for humidifyingthe respiratory gas, a sensor device for generating a signal indicativein respect of the respiratory gas humidity and a control device forcontrolling the humidification device having regard to the signal whichis generated by the sensor device and which is indicative in respect ofthe respiratory gas humidity.

In that way it is advantageously possible to match the humidity state ofthe respiratory gas in a narrow tolerance range to the instantaneousphysiological demands of the patient. In that way it is advantageouslypossible to ensure that the respiratory gas is not inadequately orexcessively humidified by virtue of an adjustment which is initiallyimplemented on the part of the patient in the context of a deep-sleepphase or upon a change in breathing characteristic.

In accordance with a particularly preferred embodiment of the inventionthe sensor device for generating a signal indicative in respect of theabsolute and/or relative humidity of the respiratory gas is arranged inthe region of a breathing mask provided for supplying the respiratorygas.

Alternatively thereto or in a particularly advantageous manner incombination with that feature it is also possible for a sensor devicefor producing a signal indicative in respect of the humidity state ofthe respiratory gas to be arranged at the outlet of an airhumidification device. By virtue of combined consideration of an airhumidity signal generated in the outlet region of an air humidificationdevice and an air humidity signal generated in the region of the patientor mask, it is then possible to check whether an unacceptably greatchange in the humidity state of the respiratory gas and in particularprecipitation of water takes place in the region of a respiratory gasconduit means provided between the breathing mask and the airhumidification device.

It is also possible, for example by a temperature detection deviceprovided in the region of the breathing mask, to detect the temperatureof the respiratory gas in the region of the patient and, on the basis ofan additional humidity signal produced for example in the region of anair humidification device, to assess whether an unacceptably highrelative humidity level obtains in the respiratory gas in the regionnear the patient. Particularly in conjunction with a sensor deviceprovided in the region of the patient for detecting a signal indicativein respect of the humidity state of the respiratory gas, it isadvantageously possible to draw a distinction between expiratoryhumidity states and inspiratory humidity states.

The humidity states ascertained for the respective breathing phases canbe taken into consideration in terms of regulating the respiratory gashumidity level, on the basis of a predetermined or preferably adaptivelymatched regulating procedure.

By virtue of the present invention it is possible to reduce theproportion of water which is entrained in drop form in the respiratorygas. That reliably avoids any germs being transported by way of drops ofwater.

In accordance with a particularly preferred embodiment of the inventionthe sensor device is arranged in the region, near a patient, of arespiratory gas conduit system. In that way it is advantageouslypossible to detect the respiratory gas humidity state which is actuallyrelevant to the user. In that respect, in a particularly advantageousconfiguration, the sensor device is arranged in the region of abreathing mask and in particular is integrated into the breathing mask.In that respect the sensor device is preferably of such a designconfiguration that the measurement dynamics thereof are considerablyhigher than the breathing rate of the patient. In that way it ispossible to specifically detect the humidity state of the respiratorygas for the respective breathing phases. The measurement values whichare detected in that way for the expiration phase and for theinspiration phase, in regard to respiratory gas humidity level, can beevaluated by a preferably adaptively optimized regulating procedure. Itis possible to disregard the respiratory gas humidity values ascertainedin respect of the expiration phase or to take them into account only ascontrol values, and to implement adjustment of the respiratory gashumidity essentially having regard to the respiratory gas humidityvalues detected in respect of the inspiration processes.

As an alternative to arranging the sensor device in the region near thepatient—or in a particularly advantageous fashion in combinationtherewith—it is possible for the sensor device or a further sensordevice to be arranged in the region between the breathing mask and ahose conduit portion, and in particular to integrate it into a couplingstructure or a washing-out valve arrangement.

The sensor device can also be arranged in the region of thehumidification device so that the humidity state of the respiratory gascan be directly detected by way of the sensor device and the operatingperformance of the humidification device can be matched in regard to adesired respiratory gas reference humidity state, having regard to theinstantaneous respiratory gas humidity level.

In accordance with a particularly preferred embodiment of the inventionthe sensor device includes an electrical sensor element, whereinprovided in the region of that sensor element is an electronic circuit,for the generation of a data sequence, by way of which the respiratorygas humidity measurement signals detected on the part of the sensorelement can be transmitted in encoded form. Processing of therespiratory gas humidity signals detected by the sensor element in theregion of the sensor element itself makes it possible substantially toavoid falsification of the signal, for example because of thetransmission properties of any signal lines.

The sensor element is preferably designed in such a way that it detectsthe respiratory gas humidity on the basis of inductive, capacitiveand/or thermal interaction effects. As an alternative thereto or also incombination with the use of physical measurement principles of thatkind, it is also possible to detect the respiratory gas humidity byoptical means.

In accordance with a particularly preferred embodiment of the inventiona signal indicative in respect of the temperature of the respiratory gasis also generated on the part of the sensor device. Insofar as that isnot the case, it is possible for a measuring device which is suitablefor detecting the temperature of the respiratory gas to be preferablyalso arranged in the immediate proximity of the sensor element.

It is possible for the sensor device for detecting the respiratory gashumidity to be arranged in the region of the humidification device andfor a temperature detection device to be provided in the region near thepatient. On the basis of the respiratory gas humidity state detected inthe region of the humidification device and the respiratory gastemperature detected in the region of the patient, it is possible todetect the relative humidity level of the respiratory gas at thepatient. The measurement values detected on the part of the temperaturedetection device or also the humidity sensor device can also be takeninto consideration in actuation of the conveyor device, besidesactuation of the humidification device. Thus, on the basis of themeasurement values generated by the humidity sensor device and/or thetemperature detection device, it is possible to implement a breathingphase recognition operation and to modulate the respiratory gas pressurein accordance with the recognized breathing phases.

The operation of ascertaining a reference respiratory gas humidity valuewhich is relevant for operation of the humidification device ispreferably effected having regard to a data set, in particular anadaptively optimized data field, which takes account of the sleep stateof the patient, the breath volume of the patient and for example alsothe position of sleep of the patient, and in particular the degree ofneck rotation thereof. Thus it is possible for example, in periods oftime in which the patient is sleeping on one side, to actuate lowerrespiratory gas humidity levels than for example in a situationinvolving a supply of respiratory gas when lying on the back.

Adjustment of the humidification output of the humidification device,such adjustment being effected in accordance with the signals generatedby the humidity sensor device, is effected preferably by altering thetemperature of the humidification water which comes into contact withthe respiratory gas.

As an alternative to or also in combination with the above-describedmeasure it is also possible to alter the humidification output of thehumidification device for example by altering the effective watersurface area available for humidification purposes. It is also possiblefor the respiratory gas temperature and in particular the temperature ofthe respiratory gas to be definedly adjusted before it comes intocontact with the humidification water.

It is also possible to alter the flow characteristic of the air cominginto contact with the humidification water, in such a way that therespectively desired respiratory gas humidity values checked by thesensor device occur at the outlet of the humidification device.

An embodiment of the invention, which is advantageous in regard toparticularly precise conditioning of the respiratory gas in respect ofthe moisture contained therein is afforded if, if necessary, only apartial flow of the respiratory gas is brought into contact with thehumidification water, wherein the respiratory gas humidity level isdetermined by way of the ratio of the partial flow of respiratory gaswhich has come into contact with the humidification water, and thepartial flow of respiratory gas which is taken past the humidificationdevice. It is possible for the conduit means to be passed through thehumidification device in such a way that a respiratory gas which ispushed back over the humidification device during an expiration phasedoes not come into contact with the humidification water.

An embodiment of the invention, which is advantageous in regard to aparticularly high level of handling comfort, is provided in that,disposed in the region of the sensor device for detecting therespiratory gas humidity is a transmitting device for wirelesstransmission of the data sequence generated in respect of therespiratory gas humidity. A transmitting device of that kind can be forexample in the form of a blue tooth transmitting device. It is alsopossible for the signals generated on the part of the sensor device tobe transmitted back to the humidification device optically, inparticular in the form of infrared signals. When using a respiratory gasconduit produced from a material which is transparent at least in theinfrared range, it is possible for the respiratory gas hose conduit tobe used as an optical waveguide, by way of which the signals generatedon the part of the sensor device can be transmitted to thehumidification device or to a control device provided for controllingthe humidification device.

The object of the invention as specified in the opening part of thisspecification is further attained in accordance with the invention by amethod of supplying a respiratory gas to a patient, in which therespiratory gas is introduced by means of a conveyor device into aconduit system leading to a patient and is humidified, wherein theconveyor device is operated in such a way that a respiratory gaspressure which is above ambient pressure at least in phase-wise mannerobtains in the air conduit system, wherein signals indicative in respectof the relative and/or absolute humidity of the respiratory gas aregenerated by means of a sensor device and the humidity of therespiratory gas is adjusted on the basis of the signals generated inthat way.

In accordance with a particularly preferred embodiment of this methodthe humidity of the respiratory gas is detected in the region near thepatient, in particular in the region of a breathing mask. In that way itis in particular possible to detect the respiratory gas humidity levelboth for the expiration phases and also for the inspiration phases andto take account of the measurement values individually obtained in thatway, in ascertaining a reference respiratory gas humidity value.

The method according to the invention and also the above-describedapparatus are particularly advantageously suitable for the artificialrespiratory and breathing therapy sector. Humidification of therespiratory gas can also be effected in particular by ultrasonicatomizers, bubble vaporizers, surface contact humidifiers and injectionsystems. The dynamics of the respiratory gas humidification operation ispreferably selected to be so high that in particular unacceptably highor also unacceptably low respiratory gas humidity values can besufficiently quickly adjusted.

In regard to regulation of the respiratory gas temperature and/or therespiratory gas humidity content, preferably the following controlparameters (X) are evaluated: the respiratory gas volume flow, therespiratory gas temperature, the humidity content of the respiratory gasin terms of relative and/or absolute humidity, levels of gasconcentration, in particular CO₂ saturation, the therapy pressure and/orthe mask pressure and/or the difference between a therapy referencepressure and the mask pressure actually occurring at the patient,polysomnographic parameters such as snoring, heart rate, oxygensaturation, body position; and ambient conditions such as air pressure,temperature and humidity and preferably also EEG-signals, in particularmeasurement values which are derived therefrom and are indicative inrespect of the sleep phase.

The respiratory gas temperature and/or the respiratory gas humidity canbe adjusted by way of the water surface area (preferably by varying theeffective water surface area in the air humidifier) and/or the amount ofwater (preferably by means of the amount of water in the air humidifier)and/or the water temperature (preferably by heating or cooling the waterand/or water molecules in the air) and/or the respiratory gastemperature (preferably by heating or cooling the respiratory air)and/or the mixing of gases (preferably by mixing various gases, forexample dry air with mist of high humidity or also by mixing gas flowsinvolving differing temperatures and/or air humidity levels and also byvariable flow resistances in the region of the air humidifier.

Further details of the invention will be apparent from the descriptionhereinafter with reference to the drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagrammatic view to illustrate the structure ofan apparatus according to the invention, and

FIG. 2 shows a regulating circuit according to the invention foradjusting the respiratory gas humidity level.

DETAILED DESCRIPTION OF THE INVENTION

The system shown in FIG. 1 for supplying a respiratory gas includes arespiratory gas conveyor device 1, a respiratory gas humidificationdevice 2 coupled thereto, and a breathing mask device 4 coupled to therespiratory gas humidification device 2 by way of a flexible hoseconduit 3 a.

The respiratory gas humidification device 2 can also be coupled in theform of what is known as a stand-alone unit to the respiratory gasconveyor device 1 by way of a preferably flexible hose conduit 3 b. Asan alternative thereto it is also possible for the respiratory gashumidification device 2 and the respiratory gas conveyor device 1 to becombined together to form an integral unit.

Disposed in the region of the conduit system which is provided to conveythe respiratory gas and which is formed by the respiratory gas conveyordevice 1, optionally the flexible hose conduit 3 b, the respiratory gashumidification device 2, the flexible hose conduit 3 a and in particularalso the breathing mask device 4, there is at least one sensor devicefor detecting the humidity state of the respiratory gas being conveyed.In the embodiment illustrated here, provided in particular in the regionof the breathing mask device 4 is a humidity sensor 5, by way of which asignal indicative in respect of the respiratory gas humidity state isgenerated and passed to a control device CPU. The control device CPU caneither be arranged in the region of the humidity sensor 5 or canpreferably be integrated into the respiratory gas humidification deviceor the respiratory gas conveyor device 1.

The respiratory gas humidification device 2 can be actuated on the basisof the signals generated on the part of the humidity sensor 5, in such away that the humidity state of the respiratory gas which is humidifiedin the respiratory gas humidification device 2 takes account, in a closetolerance range, of the instantaneous physiological needs of the personbeing afforded respiration by way of the breathing mask device 4.

In determining the reference respiratory gas humidity state which isdecisive at the present time, besides the signals generated by thehumidity sensor 5, the procedure preferably also takes account of aperformance graph or array which for example takes account of furtherpolysomnographic parameters such as for example the degree of oxygensaturation of the blood of the person to whom respiration is beingadministered, noises, in particular snoring events as well as the heartrate and the instantaneous breathing characteristic. It is alsopossible, when calculating the reference humidity state of therespiratory gas, to take account of stages in sleep, ambient conditionsas well as other physiological parameters, in particular the position inwhich the patient sleeps.

The system illustrated here has further sensor devices 5 a, 5 b by whichsignals are generated, used for defined conditioning of the respiratorygas. The sensor device 5 b involves a sensor device for generatingsignals indicative in respect of the respiratory gas temperature: bytaking account of the respiratory gas temperature signal generated onthe part of the sensor device 5 b, it is possible definedly to adapt thehumidification output of the humidification device, as is required toachieve a desired reference humidity state.

It is possible by means of the sensor 5 a provided in the region of thehumidification device 2 to detect the humidity state of the respiratorygas immediately after it has been charged with water.

By taking account of the signal generated by the sensor device 5 adisposed in the ambient region of the respiratory gas humidificationdevice and also the signal generated by the sensor device 5 in theregion near the mask, it is then possible to recognize any changes instate of the respiratory gas, caused by the flexible hose conduit 3 a,in particular the formation of condensation water in the flexible hoseconduit 3 a, and on the basis thereof to implement corrections to thehumidification output of the respiratory gas humidification device 2.

The sensor device 5 provided in the region of the breathing mask device4 preferably includes a sensor element for detecting the humidity stateon the basis of electromagnetic interactions, in particular capacitiveinteractions. The measurement signals generated by the sensor elementare preferably converted into a digital data format by a connectedmeasurement circuit while still in the region of the sensor element, andtransmitted to the CPU by way of a preferably potential-free measurementdata output.

It is possible for transmission of the humidity signals generated in theregion of the breathing mask to be implemented by way of a data linewhich is preferably integrated into the flexible hose conduit 3 a or isat least guided along same.

As an alternative thereto it is also possible for the measurementsignals generated on the part of the humidity sensor 5 to be transmittedwirelessly, for example by way of a blue tooth arrangement, to the CPUor also to other detection devices. In this case the voltage supply forthe humidity sensor 5 is preferably effected by means of a voltagesource provided in the region of the breathing mask device 4, forexample in the form of a button cell or a solar cell.

The respiratory gas humidification device 2 may include for example anultrasonic atomizing device, a bubble vaporizer or a surface contacthumidifier. Preferably the humidification output of the humidificationdevice 2 can be matched to the required humidification output within atime window which does not exceed a duration of 10 minutes.

FIG. 2 diagrammatically shows a preferred embodiment of a regulatingcircuit for controlling the humidity state of the respiratory gas. Thatregulating circuit makes it possible to individually match therespiratory gas temperature and/or the respiratory gas air humidity tothe instantaneous physiological state of the patient, that is to say toincrease it or reduce it in phase-wise manner.

Preferably the following control parameters (X) are evaluated for thepurposes of regulating the respiratory gas state:

volume flow;

respiratory gas temperature;

humidity content of the respiratory air in terms of relative and/orabsolute humidity;

levels of gas concentration (gas composition, in particular 0 ₂content);

therapy pressure and/or mask pressure and/or delta between therapypressure and the actually applied mask pressure;

polysomnographic parameters such as snoring, heart rate, oxygensaturation, body position;

ambient conditions such as air pressure, temperature and humiditycontent;

EEG (sleep phase such as NREM 1-4, REM);

mathematical control values (X_(M));

mathematical calculations from the control parameters.

Preferably the following initial parameters (Y) are regulated for therespiratory gas temperature and/or respiratory gas humidity:

water surface area (preferably by altering the effective water surfacearea in the air humidifier); and/or

amount of water (preferably by way of the amount of water which is inthe air humidifier); and/or

water temperature (preferably by heating or cooling the water and/orwater molecules in the air); and/or

respiratory gas temperature (preferably by heating or cooling therespiratory air); and/or

mixing gases (preferably by mixing various gases, for example dry airwith mist/of high humidity at differing temperatures and/or withdiffering air humidity); and/or

flow resistances (preferably by way of the flow speed in the system).

The evaluation operation is preferably effected on the basis of theevaluation algorithm described hereinafter:

1st Feature

At least one control parameter (X) or a suitable combination is requiredfor regulating the respiratory temperature and/or the respiratoryhumidity.

2nd Feature

The control parameters are evaluated over a given time interval,preferably over the expiration and inspiration time. The measurementvalues obtained in that way, within an interval, are subjected tofurther mathematical calculation, preferably maxima and/or minima and/ordelta between minimum and maximum and/or mean values.

3rd Feature

Typical behavior patterns on the part of the patients can be calculatedfrom the control parameters (X). Thus, it is possible to establish theinstantaneous breathing state by virtue of the reverse correlation ofgiven control parameters (X), for example volume flow, temperaturefluctuation in the respiration air, that is to say it is possible todraw a distinction between stable respiration (uniform amplitudes andregular respiration rate) and unstable respiration (irregular amplitudeand respiration rate, periodic respiration) and regulation can beimplemented on the basis of the mathematical control values (X_(M)).

The mode of operation of a respiratory gas supply system according tothe invention is described hereinafter.

Control Parameters:

Volume Flow:

1. If the measured volume flow exceeds a limit value (for example due tomouth leakage), an increase in the respiratory gas temperature or anincrease in respiration humidity is preferably effected. If the measuredvolume flow falls below a limit value (for example due to a low breathvolume), cooling of the respiratory gas temperature or a reduction inrespiration humidity is preferably effected.

2. A distinction can be made between stable respiration (uniformamplitude and regular respiration rate) and unstable respiration(irregular amplitude and respiration rate, periodic respiration)preferably by reverse correlation from the volume flow. The respiratorygas temperature and the respiration humidity is regulated by the resultof the reverse correlation.

Respiratory Gas Temperature:

1. If the measured respiratory gas temperature falls below a limit value(for example due to mouth leakage), an increase in the respiratory gastemperature or an increase in respiratory gas humidity is preferablyeffected. If the measured respiratory gas temperature exceeds a limitvalue (for example due to a low breath volume), cooling of therespiratory gas temperature or a reduction in respiration humidity ispreferably effected.

2. Both the temperature fluctuations during inspiration and expirationcan be evaluated. The temperature difference measured from breathing inand breathing out is used as a regulating parameter. In the case of bigbreaths (large volume flow) the temperature delta between inspirationand expiration is highly pronounced so that preferably the respiratorygas temperature or respiration humidity is increased.

3. A distinction can be made between stable respiration (uniformamplitude and regular respiration rate) and unstable respiration(irregular amplitude and respiration rate, periodic respiration)preferably by reverse correlation from the respiratory gas temperature.The respiratory gas temperature and the respiration gas humidity areregulated by the result of the reverse correlation.

Humidity:

The respiratory air humidity is measured during expiration andinspiration. Humidity measurement can be effected both relatively andalso absolutely.

1. The expiration and inspiration measurement values obtained in thatway are further mathematically calculated, preferably over a timeinterval in which the minimum and/or the maximum and/or the deltabetween minimum and maximum and/or the mean value is formed.

2. The control parameter humidity can also be combined for example independence with the ambient temperature, kind of respiration (reversecorrelation).

Initial Parameters:

Gas Concentration:

1. The respiratory gas humidity and/or the respiratory gas temperaturecan be regulated by mixing dry and humid air. Thus it is possible tobranch off the air flow so that the air is passed over the surface ofthe water and/or over the cooling/heating means.

Flow Resistance:

1. The flow resistance within the air humidifier can be altered. If forexample a high level of air humidity is required then contact or theresidence time in the humidifier can be increased by increasing the flowresistance in the air humidifier.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. An apparatus configured to deliver a flow ofbreathable gas at a continuously positive pressure with respect toambient air pressure to an entrance of a patient's airways including atleast an entrance of the patient's nares throughout the patient'srespiratory cycle while the patient is sleeping to ameliorate sleepdisordered breathing, the apparatus comprising: a blower configured topositively pressurize the breathable gas to a predetermined level; ahumidifier configured to humidify the breathable gas; and a controllerconfigured to (1) distinguish between the patient's expiratory breathingphase and the patient's inspiratory breathing phase based on at leastone breathable gas control parameter evaluated during the patient'sexpiratory breathing phase and the patient's inspiratory breathing phaseand (2) regulate humidity of the breathable gas as a function of atleast one measured inspiratory value of the at least one breathable gascontrol parameter, the at least one measured inspiratory valuecorresponding to the patient's inspiratory breathing phase, wherein thecontroller is configured to disregard measured expiratory valuesassociated with the at least one breathable gas control parameter whenregulating the humidity of the breathable gas, the measured expiratoryvalues corresponding to the patient's expiratory breathing phase.
 2. Theapparatus of claim 1, wherein the controller is configured to evaluatethe at least one breathable gas control parameter over a predeterminedtime interval that includes at least one cycle of the patient'sinspiratory breathing phase and the patient's expiratory breathingphase.
 3. The apparatus of claim 2 further comprising a patientinterface configured to sealingly engage the patient's face and deliverthe humidified breathable gas from the humidifier to the patient'sairways, wherein the at least one breathable gas control parameterincludes at least one of: volume flow of the breathable gas, temperatureof the breathable gas, humidity of the breathable gas, concentrationlevels of the breathable gas, a predetermined therapy pressure, pressureof the breathable gas at the patient interface, a difference between thepredetermined therapy pressure and the pressure of the breathable gas atthe patient interface, polysomnographic parameters of the patient,ambient conditions, sleep phase, and mathematical control values.
 4. Theapparatus of claim 3, wherein the polysomnographic parameters include atleast one of: snoring, heart rate oxygen saturation, body position andneck position.
 5. The apparatus of claim 3, wherein the ambientconditions include at least one of: air pressure, temperature andhumidity.
 6. A CPAP system configured to deliver a flow of breathablegas at a continuously positive pressure with respect to ambient airpressure to an entrance of a patient's airways including at least anentrance of the patient's nares throughout the patient's respiratorycycle while the patient is sleeping to ameliorate sleep disorderedbreathing, the CPAP system comprising: the apparatus of claim 1; apatient interface configured to sealingly engage an area adjacent theentrance to the patient's airways; and an air circuit configured todeliver the breathable gas to the patient interface.
 7. The CPAP systemof claim 6, further comprising a sensing device positioned at thepatient interface and in communication with the controller of theapparatus, the sensing device being configured to sense at least one ofhumidity and temperature of the breathable gas.
 8. A method fordelivering a flow of breathable gas at a continuously positive pressurewith respect to ambient air pressure to an entrance of a patient'sairways including at least an entrance of the patient's nares throughoutthe patient's respiratory cycle while the patient is sleeping toameliorate sleep disordered breathing, the method comprising: positivelypressurizing the breathable gas to a predetermined level; distinguishingbetween the patient's expiratory breathing phase and the patient'sinspiratory breathing phase based on at least one breathable gas controlparameter evaluated during the patient's expiratory breathing phase andthe patient's inspiratory breathing phase; regulating humidity of thebreathable gas as a function of at least one measured inspiratory valueof the at least one breathable gas control parameter, the at least onemeasured inspiratory value corresponding to the patient's inspiratorybreathing phase; and delivering the breathable gas to the patient,wherein measured expiratory values associated with the at least onebreathable gas control parameter are disregarded when regulating thehumidity of the breathable gas, the measured expiratory valuescorresponding to the patient's expiratory breathing phase.
 9. The methodof claim 8, wherein the at least one breathable gas control parameter isevaluated over a predetermined time interval that includes at least onecycle of the patient's inspiratory breathing phase and the patient'sexpiratory breathing phase.
 10. The method of claim 9, wherein the atleast one breathable gas control parameter includes at least one of:volume flow of the breathable gas, temperature of the breathable gas,humidity of the breathable gas, concentration levels of the breathablegas, a predetermined therapy pressure, pressure of the breathable gas ata patient interface, a difference between the predetermined therapypressure and the pressure of the breathable gas at the patientinterface, polysomnographic parameters of the patient, ambientconditions, sleep phase, and mathematical control values.
 11. The methodof claim 10, wherein the polysomnographic parameters include at leastone of: snoring, heart rate oxygen saturation, body position and neckposition.
 12. The method of claim 10, wherein the ambient conditionsinclude at least one of: air pressure, temperature and humidity.
 13. Anapparatus configured to deliver a flow of breathable gas at acontinuously positive pressure with respect to ambient air pressure toan entrance of a patient's airways including at least an entrance of thepatient's nares throughout the patient's respiratory cycle while thepatient is sleeping to ameliorate sleep disordered breathing, theapparatus comprising: a blower configured to positively pressurize thebreathable gas to a predetermined level; a humidifier configured tohumidify the breathable gas; a sensing device configured to sensehumidity of the pressurized breathable gas; and a controller configuredto (1) distinguish between the patient's expiratory humidity state andthe patient's inspiratory humidity state based on humidity values sensedby the sensing device during the patient's inspiratory and expiratorybreathing phases and (2) regulate humidity of the pressurized breathablegas based on the inspiratory humidity state, wherein the controller isconfigured to disregard the humidity values sensed by the sensing deviceduring the patient's expiratory breathing phase when regulating thehumidity of the breathable gas.
 14. The apparatus of claim 13, whereinthe controller is configured to distinguish between the patient'sexpiratory and inspiratory humidity states based on maxima and/or minimahumidity levels sensed by the sensing device.
 15. The apparatus of claim13 further comprising a patient interface configured to sealingly engagethe patient's face and deliver the humidified breathable gas from thehumidifier to the patient's airways, wherein the controller isconfigured to determine the expiratory humidity state and theinspiratory humidity state based on at least one breathable gas controlparameter, the at least one breathable gas control parameter includingat least one of: volume flow of the breathable gas, temperature of thebreathable gas, humidity of the breathable gas, concentration levels ofthe breathable gas, a predetermined therapy pressure, pressure of thebreathable gas at the patient interface, a difference between thepredetermined therapy pressure and the pressure of the breathable gas atthe patient interface, polysomnographic parameters of the patient,ambient conditions, sleep phase, and mathematical control values. 16.The apparatus of claim 15, wherein the polysomnographic parametersinclude at least one of: snoring, heart rate oxygen saturation, bodyposition and neck position.
 17. The apparatus of claim 15, wherein theambient conditions include at least one of: air pressure, temperatureand humidity.
 18. A CPAP system configured to deliver a flow ofbreathable gas at a continuously positive pressure with respect toambient air pressure to an entrance of a patient's airways including atleast an entrance of the patient's nares throughout the patient'srespiratory cycle while the patient is sleeping to ameliorate sleepdisordered breathing, the CPAP system comprising: the apparatus of claim13; a patient interface configured to sealingly engage an area adjacentthe entrance to the patient's airways; and an air circuit configured todeliver the breathable gas to the patient interface.
 19. The CPAP systemof claim 18, wherein the sensing device is positioned at the patientinterface.